Standard for quantification

Ion implantation is often used to produce reliable standards for quantification of SIMS analyses. Ion implantation allows the introducdon of a known amount of an element into a solid sample. A sample with a major component composition similar to that of the unknown sample may be implanted to produce an accurate standard. The accuracy of quandfication using this implantation method can be as good as 2%. 

In both the GC/MS and the LC-FL analyses selected perdeuterated PAHs were added to the samples prior to extraction for use as internal standards for quantification. 

Chemicals quality of deionized water and chemicals for buffer preparation and rinsing, standards for quantification and selectivity verification, test samples, correct transport and storage conditions... 

Figure 1.18. Comparison of MRM chromatograms following HPLC-MS/MS and UPLC-MS/ MS analysis of a mixture containing alprazolam, ibuprofen, d5-alprazolam, diphenhydramine, naproxen, and prednisolone. Each set of chromatograms was obtained from a single 100-ng/ mL injection of rat plasma. d5-Alprazolam was used as the internal standard for quantification of alprazolam. (Reprinted with pemnission from Yu et al., 2006.)...

MALDI target for analysis. All data points were collected into one data file for clarity and speed. An example of a MALDI target prepared by eluant spotting is shown in Fig. 11.8. Figure 11.9 shows a microsome time course for a typical analyte, internal standard, and analyte-intemal standard ratio. This example illustrates the necessity of the internal standard for quantification. Half-lives were calculated for all compounds from both data sets. The half-lives obtained by the two ionization methods are plotted in Fig. 11.10. A good correlation was obtained between the two techniques. 

There are important limitations in understanding the spatial and temporal trend of the pollutant levels of waterbirds, which is particularly true in China. Many studies that have been conducted in China have focused on water and sediment. There is limited information of pollutant levels in waterbirds available in China. In addition, a number of studies have investigated target pollutants with different tissue samples of different species. It has been determined that different tissue samples of species of birds can accumulate varying degrees of pollutants. It would be more instructive to compare tissue samples within species. Moreover, it is difficult to adequately compare current results with previous ones (i.e. 1940s-1970s) because of the advanced capability and improved sensitivity of instruments, and the application of different extraction methods and standards for quantification. 

Lee, M. G. Millard, B. J. 1975. A comparison of unlabelled and labelled internal standards for quantification by single and multiple ion monitoring. /. Biomed. Mass Spectrom., 2,78-81. 

Commonly used techniques for this purpose are chromatography and hyphenated methods, mostly coupled with element-specific detection, for example, GC-AED,221 GC coupled with atomic absorption detection (GC-AAS),222 or ICP-MS. The last mentioned provides superior sensitivity as well as the possibility of using isotopically labeled standards for quantification and quality control.223... 

FIGURE 4 (A) The use of stable isotope internal standards for quantification of Phe extracted... 

The availability of single standards for quantification of toxaphene resulted in the following results and conclusions ... 

This observation most likely leads to a slight underestimation of endogenous all trans retinoic acid in plasma, when using the 13-cis retinoic acid internal standard for quantification. 

We have developed a very sensitive assay which can quantify both 13-cis and all trans retinoic acid in the same plasma sample. Only 1 ml of plasma is necessary for analysis, with a limit of quantification of 0.5 ng/ml. The assay is linear for both cis and trans retinoic acid, and there is virtually no interconversion of the two isomers by assay manipulations. However, the assay does slightly underestimate the amount of all trans retinoic acid present due to the differential recovery of this isomer from plasma as opposed to recovery from PBS. This will be corrected in future work by the addition of a stable isotope labelled all trans retinoic acid internal standard for quantification. 

Farley JR, Hall SL, Herring S, Libanati C, Wergedal JE. Reference standards for quantification of skeletal alkaline phosphatase activity in serum by heat inactivation and lectin precipitation. Clin Chem 1993 39 1878-84. 

Savonet, V., C. Maenhaut, F. Miot and I. Pirson. Pitfalls in the use of several housekeeping genes as standards for quantification of mRNA the example of thyroid cells. Anal. Biochem. 247 165-167, 1997. 

DNA isolation from any tissue of interest after compound administration followed by (1) addition of stable isotope-labeled internal standard for quantification, (2) hydrolysis/ digestion of DNA, (3) enrichment of DNA adducts of interest (e.g., solid-phase extraction, immunoaffinity chromatography, or DNA repair enzymes),... 

Internal Reference Standards for Quantification and the Evaluation of Sample Preparation... 

Figure 16.1. Kinetics of H/D exchange of the C2-H in pyruvate decarboxylase from Saccharomyces cerevisiae. The H NMR spectra are expansions showing the ThDP signals C2-H at 9.55 ppm and C6 -H at 7.85 ppm as a nonexchanging standard for quantification.

Turnipseed et al. described a method for the multi-class residue determination of P-Iactams, sulfonamides, tetracyclines, fluoroquinolones, and macroiides in milk and other dairy products. The sample preparation combines extraction with acetonitrile, clean-up with Oasis HLB cartridges, and ultrafiltration using molecular weight cut-off filters to improve the overall performance of the analysis. Acceptable recoveries were obtained for sulfanomides, macroiides, and quinolones (>70%) however, recoveries were rather low for tetracyclines (50-60%) and P-lactams (<50%). Despite the extensive clean-up procedure, significant matrix ion suppression was observed for many compounds, making it necessary to include matrix-matched calibration standards for quantification purposes. 

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